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Revision 1.54 by root, Tue Nov 27 20:26:51 2007 UTC vs.
Revision 1.61 by root, Thu Nov 29 12:21:05 2007 UTC

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63details of the event, and then hand it over to libev by I<starting> the 63details of the event, and then hand it over to libev by I<starting> the
64watcher. 64watcher.
65 65
66=head1 FEATURES 66=head1 FEATURES
67 67
68Libev supports C<select>, C<poll>, the linux-specific C<epoll>, the 68Libev supports C<select>, C<poll>, the Linux-specific C<epoll>, the
69bsd-specific C<kqueue> and the solaris-specific event port mechanisms 69BSD-specific C<kqueue> and the Solaris-specific event port mechanisms
70for file descriptor events (C<ev_io>), relative timers (C<ev_timer>), 70for file descriptor events (C<ev_io>), the Linux C<inotify> interface
71(for C<ev_stat>), relative timers (C<ev_timer>), absolute timers
71absolute timers with customised rescheduling (C<ev_periodic>), synchronous 72with customised rescheduling (C<ev_periodic>), synchronous signals
72signals (C<ev_signal>), process status change events (C<ev_child>), and 73(C<ev_signal>), process status change events (C<ev_child>), and event
73event watchers dealing with the event loop mechanism itself (C<ev_idle>, 74watchers dealing with the event loop mechanism itself (C<ev_idle>,
74C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as 75C<ev_embed>, C<ev_prepare> and C<ev_check> watchers) as well as
75file watchers (C<ev_stat>) and even limited support for fork events 76file watchers (C<ev_stat>) and even limited support for fork events
76(C<ev_fork>). 77(C<ev_fork>).
77 78
78It also is quite fast (see this 79It also is quite fast (see this
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162C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for 163C<ev_embeddable_backends () & ev_supported_backends ()>, likewise for
163recommended ones. 164recommended ones.
164 165
165See the description of C<ev_embed> watchers for more info. 166See the description of C<ev_embed> watchers for more info.
166 167
167=item ev_set_allocator (void *(*cb)(void *ptr, size_t size)) 168=item ev_set_allocator (void *(*cb)(void *ptr, long size))
168 169
169Sets the allocation function to use (the prototype and semantics are 170Sets the allocation function to use (the prototype is similar - the
170identical to the realloc C function). It is used to allocate and free 171semantics is identical - to the realloc C function). It is used to
171memory (no surprises here). If it returns zero when memory needs to be 172allocate and free memory (no surprises here). If it returns zero when
172allocated, the library might abort or take some potentially destructive 173memory needs to be allocated, the library might abort or take some
173action. The default is your system realloc function. 174potentially destructive action. The default is your system realloc
175function.
174 176
175You could override this function in high-availability programs to, say, 177You could override this function in high-availability programs to, say,
176free some memory if it cannot allocate memory, to use a special allocator, 178free some memory if it cannot allocate memory, to use a special allocator,
177or even to sleep a while and retry until some memory is available. 179or even to sleep a while and retry until some memory is available.
178 180
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703events but its callback has not yet been invoked). As long as a watcher 705events but its callback has not yet been invoked). As long as a watcher
704is pending (but not active) you must not call an init function on it (but 706is pending (but not active) you must not call an init function on it (but
705C<ev_TYPE_set> is safe) and you must make sure the watcher is available to 707C<ev_TYPE_set> is safe) and you must make sure the watcher is available to
706libev (e.g. you cnanot C<free ()> it). 708libev (e.g. you cnanot C<free ()> it).
707 709
708=item callback = ev_cb (ev_TYPE *watcher) 710=item callback ev_cb (ev_TYPE *watcher)
709 711
710Returns the callback currently set on the watcher. 712Returns the callback currently set on the watcher.
711 713
712=item ev_cb_set (ev_TYPE *watcher, callback) 714=item ev_cb_set (ev_TYPE *watcher, callback)
713 715
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741 { 743 {
742 struct my_io *w = (struct my_io *)w_; 744 struct my_io *w = (struct my_io *)w_;
743 ... 745 ...
744 } 746 }
745 747
746More interesting and less C-conformant ways of catsing your callback type 748More interesting and less C-conformant ways of casting your callback type
747have been omitted.... 749instead have been omitted.
750
751Another common scenario is having some data structure with multiple
752watchers:
753
754 struct my_biggy
755 {
756 int some_data;
757 ev_timer t1;
758 ev_timer t2;
759 }
760
761In this case getting the pointer to C<my_biggy> is a bit more complicated,
762you need to use C<offsetof>:
763
764 #include <stddef.h>
765
766 static void
767 t1_cb (EV_P_ struct ev_timer *w, int revents)
768 {
769 struct my_biggy big = (struct my_biggy *
770 (((char *)w) - offsetof (struct my_biggy, t1));
771 }
772
773 static void
774 t2_cb (EV_P_ struct ev_timer *w, int revents)
775 {
776 struct my_biggy big = (struct my_biggy *
777 (((char *)w) - offsetof (struct my_biggy, t2));
778 }
748 779
749 780
750=head1 WATCHER TYPES 781=head1 WATCHER TYPES
751 782
752This section describes each watcher in detail, but will not repeat 783This section describes each watcher in detail, but will not repeat
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885=item ev_timer_again (loop) 916=item ev_timer_again (loop)
886 917
887This will act as if the timer timed out and restart it again if it is 918This will act as if the timer timed out and restart it again if it is
888repeating. The exact semantics are: 919repeating. The exact semantics are:
889 920
921If the timer is pending, its pending status is cleared.
922
890If the timer is started but nonrepeating, stop it. 923If the timer is started but nonrepeating, stop it (as if it timed out).
891 924
892If the timer is repeating, either start it if necessary (with the repeat 925If the timer is repeating, either start it if necessary (with the
893value), or reset the running timer to the repeat value. 926C<repeat> value), or reset the running timer to the C<repeat> value.
894 927
895This sounds a bit complicated, but here is a useful and typical 928This sounds a bit complicated, but here is a useful and typical
896example: Imagine you have a tcp connection and you want a so-called 929example: Imagine you have a tcp connection and you want a so-called idle
897idle timeout, that is, you want to be called when there have been, 930timeout, that is, you want to be called when there have been, say, 60
898say, 60 seconds of inactivity on the socket. The easiest way to do 931seconds of inactivity on the socket. The easiest way to do this is to
899this is to configure an C<ev_timer> with C<after>=C<repeat>=C<60> and calling 932configure an C<ev_timer> with a C<repeat> value of C<60> and then call
900C<ev_timer_again> each time you successfully read or write some data. If 933C<ev_timer_again> each time you successfully read or write some data. If
901you go into an idle state where you do not expect data to travel on the 934you go into an idle state where you do not expect data to travel on the
902socket, you can stop the timer, and again will automatically restart it if 935socket, you can C<ev_timer_stop> the timer, and C<ev_timer_again> will
903need be. 936automatically restart it if need be.
904 937
905You can also ignore the C<after> value and C<ev_timer_start> altogether 938That means you can ignore the C<after> value and C<ev_timer_start>
906and only ever use the C<repeat> value: 939altogether and only ever use the C<repeat> value and C<ev_timer_again>:
907 940
908 ev_timer_init (timer, callback, 0., 5.); 941 ev_timer_init (timer, callback, 0., 5.);
909 ev_timer_again (loop, timer); 942 ev_timer_again (loop, timer);
910 ... 943 ...
911 timer->again = 17.; 944 timer->again = 17.;
912 ev_timer_again (loop, timer); 945 ev_timer_again (loop, timer);
913 ... 946 ...
914 timer->again = 10.; 947 timer->again = 10.;
915 ev_timer_again (loop, timer); 948 ev_timer_again (loop, timer);
916 949
917This is more efficient then stopping/starting the timer eahc time you want 950This is more slightly efficient then stopping/starting the timer each time
918to modify its timeout value. 951you want to modify its timeout value.
919 952
920=item ev_tstamp repeat [read-write] 953=item ev_tstamp repeat [read-write]
921 954
922The current C<repeat> value. Will be used each time the watcher times out 955The current C<repeat> value. Will be used each time the watcher times out
923or C<ev_timer_again> is called and determines the next timeout (if any), 956or C<ev_timer_again> is called and determines the next timeout (if any),
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1192not exist" is a status change like any other. The condition "path does 1225not exist" is a status change like any other. The condition "path does
1193not exist" is signified by the C<st_nlink> field being zero (which is 1226not exist" is signified by the C<st_nlink> field being zero (which is
1194otherwise always forced to be at least one) and all the other fields of 1227otherwise always forced to be at least one) and all the other fields of
1195the stat buffer having unspecified contents. 1228the stat buffer having unspecified contents.
1196 1229
1230The path I<should> be absolute and I<must not> end in a slash. If it is
1231relative and your working directory changes, the behaviour is undefined.
1232
1197Since there is no standard to do this, the portable implementation simply 1233Since there is no standard to do this, the portable implementation simply
1198calls C<stat (2)> regulalry on the path to see if it changed somehow. You 1234calls C<stat (2)> regularly on the path to see if it changed somehow. You
1199can specify a recommended polling interval for this case. If you specify 1235can specify a recommended polling interval for this case. If you specify
1200a polling interval of C<0> (highly recommended!) then a I<suitable, 1236a polling interval of C<0> (highly recommended!) then a I<suitable,
1201unspecified default> value will be used (which you can expect to be around 1237unspecified default> value will be used (which you can expect to be around
1202five seconds, although this might change dynamically). Libev will also 1238five seconds, although this might change dynamically). Libev will also
1203impose a minimum interval which is currently around C<0.1>, but thats 1239impose a minimum interval which is currently around C<0.1>, but thats
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1205 1241
1206This watcher type is not meant for massive numbers of stat watchers, 1242This watcher type is not meant for massive numbers of stat watchers,
1207as even with OS-supported change notifications, this can be 1243as even with OS-supported change notifications, this can be
1208resource-intensive. 1244resource-intensive.
1209 1245
1210At the time of this writing, no specific OS backends are implemented, but 1246At the time of this writing, only the Linux inotify interface is
1211if demand increases, at least a kqueue and inotify backend will be added. 1247implemented (implementing kqueue support is left as an exercise for the
1248reader). Inotify will be used to give hints only and should not change the
1249semantics of C<ev_stat> watchers, which means that libev sometimes needs
1250to fall back to regular polling again even with inotify, but changes are
1251usually detected immediately, and if the file exists there will be no
1252polling.
1212 1253
1213=over 4 1254=over 4
1214 1255
1215=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval) 1256=item ev_stat_init (ev_stat *, callback, const char *path, ev_tstamp interval)
1216 1257
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1985 2026
1986=item EV_USE_DEVPOLL 2027=item EV_USE_DEVPOLL
1987 2028
1988reserved for future expansion, works like the USE symbols above. 2029reserved for future expansion, works like the USE symbols above.
1989 2030
2031=item EV_USE_INOTIFY
2032
2033If defined to be C<1>, libev will compile in support for the Linux inotify
2034interface to speed up C<ev_stat> watchers. Its actual availability will
2035be detected at runtime.
2036
1990=item EV_H 2037=item EV_H
1991 2038
1992The name of the F<ev.h> header file used to include it. The default if 2039The name of the F<ev.h> header file used to include it. The default if
1993undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This 2040undefined is C<< <ev.h> >> in F<event.h> and C<"ev.h"> in F<ev.c>. This
1994can be used to virtually rename the F<ev.h> header file in case of conflicts. 2041can be used to virtually rename the F<ev.h> header file in case of conflicts.
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2049=item EV_PID_HASHSIZE 2096=item EV_PID_HASHSIZE
2050 2097
2051C<ev_child> watchers use a small hash table to distribute workload by 2098C<ev_child> watchers use a small hash table to distribute workload by
2052pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more 2099pid. The default size is C<16> (or C<1> with C<EV_MINIMAL>), usually more
2053than enough. If you need to manage thousands of children you might want to 2100than enough. If you need to manage thousands of children you might want to
2054increase this value. 2101increase this value (I<must> be a power of two).
2102
2103=item EV_INOTIFY_HASHSIZE
2104
2105C<ev_staz> watchers use a small hash table to distribute workload by
2106inotify watch id. The default size is C<16> (or C<1> with C<EV_MINIMAL>),
2107usually more than enough. If you need to manage thousands of C<ev_stat>
2108watchers you might want to increase this value (I<must> be a power of
2109two).
2055 2110
2056=item EV_COMMON 2111=item EV_COMMON
2057 2112
2058By default, all watchers have a C<void *data> member. By redefining 2113By default, all watchers have a C<void *data> member. By redefining
2059this macro to a something else you can include more and other types of 2114this macro to a something else you can include more and other types of
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2119 2174
2120=item Starting io/check/prepare/idle/signal/child watchers: O(1) 2175=item Starting io/check/prepare/idle/signal/child watchers: O(1)
2121 2176
2122=item Stopping check/prepare/idle watchers: O(1) 2177=item Stopping check/prepare/idle watchers: O(1)
2123 2178
2124=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % 16)) 2179=item Stopping an io/signal/child watcher: O(number_of_watchers_for_this_(fd/signal/pid % EV_PID_HASHSIZE))
2125 2180
2126=item Finding the next timer per loop iteration: O(1) 2181=item Finding the next timer per loop iteration: O(1)
2127 2182
2128=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd) 2183=item Each change on a file descriptor per loop iteration: O(number_of_watchers_for_this_fd)
2129 2184

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